Audio and video signal distribution system and method

ABSTRACT

A system for distributing one of a plurality of input signals from one location in a building having standard AC power to another location in the building. An input signal is selected by a switcher and, if it is an analog signal, it is converted to a digital signal. The digital signal is then processed to enable it to be superimposed on, and transmitted over, an AC power line to the other location. At the other location the transmitted digital signal is processed again to restore it to its original digital format at which time it can be passed directly to a digital amplifier or converted to an analog signal for further processing.

BACKGROUND OF THE INVENTION

This invention relates to the distribution of output signals from acentral location to one or more remote locations and, more particularly,to the distribution of digital signals in this manner.

An application of the present invention is in home audio and videoentertainment systems in which one or more source components, such as acassette deck, a phonograph record, an FM tuner, and/or a VCR arelocated in one room of the house along with loudspeakers for reproducingtheir output signals. In order to reproduce these signals throughloudspeakers located in other rooms of the house, speaker wire has to berun from the components, through one or more walls of the house and tothe remote loudspeakers. Unless the house is prewired in this mannerduring construction, it is often very difficult to do this, and, even ifit is done, it often results in unsightly speaker wire being exposed.

Other problems with these systems are encountered when one or more ofthe source components produce digital output signals such as in the caseof laser disc players, compact disc players and digital audio tapedecks, since these signals cannot be treated in the same manner as theanalog signals discussed above.

BACKGROUND OF THE INVENTION

It is therefore an object of the present invention to provide a systemand method for transmitting audio and video signals from one or moreprogram sources to one or more remote locations.

It is a further object of the present invention to provide a system andmethod of the above type in which the source signals can be both analogand digital signals.

It is a still further object of the present invention to provide asystem and method of the above type in which the analog source signalsare converted to digital signals and transmitted, with the digitalsource signals, to the remote location.

It is a still further object of the present invention to provide adigital amplifier and digital-to-analog converter at the remote locationthat receive the transmitted digital signals and connect to theloudspeaker to drive same.

Toward the fulfillment of these and other objects, according to thesystem and method of the present invention, the input sources areconnected to a processor/converter that converts the analog signals todigital signals and retains the original digital source signals in theiroriginal form. Both the converted and the original digital signals arecombined and transmitted to the remote location. A processor/amplifieris provided at the remote location that functions to receive thetransmitted digital signals, restore the signals to their original formand amplify them. The signals are then passed to a digital-to-analogconverter for converting the signals to analog signals which are thentransmitted to loudspeakers at the remote location.

BRIEF DESCRIPTION OF THE DRAWINGS

The above brief description, as well as further objects, features andadvantages of the present invention will be more fully appreciated byreference to the following detailed description of the presentlypreferred but nonetheless illustrative embodiments in accordance withthe present invention when taken in conjunction with the accompanyingdrawing which is a schematic view of the system of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The drawing depicts the system of the present invention installed in ahouse having three input sources 10, 12 and 14 located in one room ofthe house. Each input source 10, 12 and 14 can be either an analogsource, such as a phonograph record player, and/or an FM tuner or ananalog cassette deck; or a digital source, such as a compact disc playeror a digital audio tape deck. The system of the present inventionincludes a switcher/converter unit 16 connected to the sources 10, 12and 14 by standard "interconnect" cables 10a, 12a and 14a, respectively,which can be the same cables that would be used to connect the sourcesto an amplifier, preamplifier or stereo receiver in a typical homeinstallation. Although each input source produces a stereo (left andright) audio signal in a conventional manner only one cable is shown inthe interest of clarity. Of course, if surround sound is involved atleast two additional audio signals would be involved and, if video isinvolved, such as in case if one of the sources is a VCR, a satellitedish or a laser disc player, an additional video signal would beinvolved. For the purposes of example, it will be assumed that the inputsource 10 is an analog cassette deck and the source 12 is an analog FMtuner, each of which produces two (stereo) analog output signals; whilethe source 14 is a digital compact disc player, which produces two(stereo) digital output signals.

The switcher/converter unit 16 has multiple functions. First, itincludes a signal switching system for selecting one of the stereooutput signals from the sources 10, 12 and 14 for processing. It alsoincludes a conventional analog-to-digital converter for converting theselected analog signal received from any of the sources 10, 12 and 14 toa digital signal, which in the present example would be the sources 10and 12. If the selected source signal is digital, which, in the examplewould be the compact disc player 14, then the latter signal is notfurther processed by the unit 16. After the above switching andconverting the two (stereo) digital signals are then passed from theoutput terminals of the unit 16, via two cables, one of which is shownby the reference numeral 18, to a processor 20 for further processing tocondition them to be transferred to a remote location. This transferprocess can be done in any known manner such as in the manner taught inU.S. Pat. No. 4,829,570 the disclosure of which is hereby incorporatedby reference, with the exception that the processor 20 would receivedigital signals from the unit 16 in the present invention as opposed toanalog signals per the latter patent.

According to the technique disclosed in the '570 patent, which alsoapplies to the present invention, the stereo signals are each initiallyamplified in the processor, then compressed to reduce their dynamicrange after which they are pre-emphasized to increase the signalstrength of the higher frequency signals included in the compressedaudio signals supplied by the compressing circuit. The signals are thenconverted into two separate FM (frequency modulation) signals byvariable frequency oscillators operating at two different carrierfrequencies after which the signals are passed through a tuned networkand then to one end of a standard AC (alternating current) cable 20a. Aplug 20b is provided on the other end of the cable and is adapted forinsertion into a standard household AC power outlet 22 connected to aconventional AC power line 24 for the household that extends to theremote location. Thus, the cable 20a transmits the two processed digitalsignals to the remote location.

A unit 26 is provided at the remote location and is adapted to receivethe transmitted digital signals from the AC power line 24, process thedigital signals in a manner to restore the signals to their originalform in a manner to be described, convert the digital signals to analogsignals, and amplify the signals. To this end, the unit 26 is connectedto the AC power line 24 by a cable 26a connected at one end to the unit26 and at the other end to an AC plug 26b which is inserted into astandard outlet 28 connected to the power line 24 at the remotelocation. Thus, the digital signals from the unit 16 are transmitted tothe unit 26 via the power line 24.

The unit 26 operates in an identical manner disclosed in theabove-identified patent to restore the processed digital signals totheir original form and, as such, contains a filter circuit forfiltering any 60 Hz AC power signal while passing the two FM digitalsignals. The two outputs from the filter circuit are amplified andadditionally filtered in the unit 26 before being demodulated by a phaseloop detector to provide two (stereo) digital outputs. The lattersignals are then de-emphasized in the unit 26 and then expanded to theiroriginal dynamic range by an expander circuit.

According to a feature of the present invention which is not disclosedin the '570 patent, two digital amplifiers are included in the unit 26which respectively amplify the two restored signals to levels sufficientto drive two loudspeakers. To this end, the restored signals in the unitare then converted to analog signals and amplified to a level to driveloudspeakers, in a conventional manner. The unit 26 has two (stereo)outputs which are connected to the input terminals of two loudspeakers28a and 28b, respectively, also located at the remote location.According to a feature of the present invention, a pair of jacks 30a and30b are provided on the output terminals of the unit 26 and are directlyconnected to corresponding jacks or terminals on the loudspeakers 28aand 28b. For example, the jacks 30a and 30b could be male plugs and thecorresponding terminals on the loudspeakers 28a and 28b could be femalereceptacles. Thus, unit 26 is connected directly to the loudspeakers 28aand 28b thus eliminating the need for cables, wires or the like.

As a result of all of the foregoing, the loudspeakers 28a and 28b aredriven by the restored analog left channel audio signal received fromthe selected input source 10, 12 or 14, and the loudspeaker 36 is drivenby the restored right channel stereo audio signal, after the processing,transmission and amplification discussed above.

Thus, the system and method thus described enjoys the advantages ofenabling one of a plurality of analog and digital sources to beselected, the analog signals converted to digital and the digitalsignals transmitted to a remote location. Also, it permits thetransmitted digital signals to be restored to their original form at theremote location, amplified and converted to analog signals, for drivingone or more loudspeakers. Also the unit 16 can be mounted in theloudspeakers at the remote location thus eliminating the need forrelative long cables or wires.

It is understood that the present invention is not limited to theprocessing of two stereo signals as described above for the purposes ofexample only. For example, the invention lends itself to multichannelaudio applications such as five or six channel surround sound systemsand audio and video applications such as in the case of home theaterinstallations.audio. Also, the units 20 and 26 can have separate powercables for connection to the power line 24 to supply AC power to theunits in a conventional manner, or the latter connections can be madethrough the cables 20a and 26a, respectively. Further, the unit 26 canbe installed in the interior of one of the loudspeakers 28a or 28b inwhich case the cable 26a would extend to the loudspeaker and aconnection made from the latter loudspeaker to the other loudspeaker.Also the unit 26 can be divided into two separate modules which areconnected to, or installed within, the loudspeakers 28a and 28b in themanner discussed above. Further, the unit 26 can be used for restoringthe digital signals to their original form in the manner discussed aboveand two separate converters and amplifiers can be provided to performthe conversion and amplification discussed above. It is understood thatother techniques can be utilized to transfer the digital signals fromthe source location to the remote location. For example, the techniquedisclosed in U.S. Pat. No. 5,327,230 can be used, the disclosure of thispatent hereby being incorporated by reference.

Still other variations may be made in the present invention by thoseskilled in the art without departing from the invention as defined inthe appended claims.

What is claimed is:
 1. In a system having a plurality of sources ofdigital and analog signals in one location in a building having standardAC power lines and one or more units for utilizing the signals inanother location in the building, wherein the improvement comprises aswitcher for selecting one of the sources at the one location, aconvertor for converting any selected analog signal into a correspondingdigital signal, a processor for processing the digital signal to enableit to be superimposed on and transmitted over an AC power line to saidsecond location, means for receiving the transmitted digital signal fromsaid AC power line at said second location and restoring the digitalsignal to its original form, and a convertor located at the otherlocation for converting the restored digital signal to an analog signalfor use at the other location.
 2. A method of selectively distributingthe digital and analog signals from one of a plurality of input sourcesin one location in a building having standard AC power lines to one ormore units for utilizing the signals in another location in thebuilding, the method comprising the steps of selecting one of the inputsources for distribution, determining if the selected input source is ananalog or digital signal and, if an analog signal, converting it to acorresponding digital signal, processing the digital signal to enable itto be superimposed on and transmitted over an AC power line to saidother location, receiving the transmitted digital signal from said ACpower line at said other location, restoring the transmitted digitalsignal to its original form, and converting the restored digital signalto an analog signal for use at the second location.